Telephone reverting call system



Nov. 17, 1953 G. ELLIOTT 2,659,769

TELEPHONE REVERTING CALL. SYSTEM D/G/T @E6/.STER

COUNTER 057' 0/6/7' ONLY JE/VDER HST 0/6/7' ONLY INVENTOR. GEORGE El. L/07'7' /7 TTORNEY Nov. 17, 1953 G. ELLIOTT TELEPHONE REVERTING CALLSYSTEM 5 Sheets-Sheet 2 Filed sept. so. 1949 INPI 6'6 INVENTOR. @E0/96EELL/077 l I I I Vu I I I I I T I'l I I l I V El REVERT/NG CFLL SW/TCHC/lPCl//T Nov. 17, 1953 G. ELLIOTT 2,659,769

TELEPHONE REVERTING CALL SYSTEM Filed Sept. 50, 1949 5 Sheets-Sheet 3ETTORNEV Nov. 17, 1953 G. ELLIOTT 2,659,769

TELEPHONE REVERTING CALL SYSTEM Filed sept. s, 1949 5 sheets-sheet 4INVENTOR. GEORGE ELL/077' 60N/viera@ 3;). e A7.' 7, 2Q

HTTOR/VE Y Nov. 17, 1953 G. ELLIOTT TELEPHONE REVERTING CALL. SYSTEMFiled Sept. 30, 1949 5 Sheets-Sheet 5 h\\ 7'/ s I ,2 I4-I+I ov n-o-K T5g l r3 I |I+I l l I I cn. I I l l4. I+I 0T- I I I |*-I+I (+I I I I I I(+I I I I I I I I I I I I /fvr/ EIZI l I I I /Nrz 'I E; H I I I I-I TT-W l m I I II I I /24 aE/v. l //v7.'4 I I I 2LH I l /lvrJ I I I 1, i II I I I I I I I I I I I I I I I I I I I I l l n I I I I I I l I E I IGEM! I GEA/.2| GEMS I G'VA# IGEMS q I I I I l I I N TIT IJ-r TIT fJLI-,

| I CMMON RING/N5 /Nrfnm/PTER c/Rcu/T 1- Rar I u u INVENTOR. GEORGEELL/07T 77 5 C BY co/v/vE TOR www f. 7M

HTTOR/VEY Patented Nov. 17, 1953 TELEPHONE REVERTING CALL SYSTEM GeorgeElliott, Rochester, N. Y., assignor to Stromberg-Carlson Company, acorporation of New York Application September 30, 1949, Serial No.118,763

26 Claims. 1

'I'he present invention relates to telephone reverting call systems andit more particularly pertains to improved apparatus and circuits forsetting up reverting call connections between two substations associatedwith the same party line.

Two methods of handling reverting calls are extensively used in systemsof the automatic type. According to one of these methods, commonly knownas the directory number dialling method, the calling subscriber, afterdialling the directory number of the called substation, restores thereceiver to its supporting hook or cradle and, after waiting areasonable time, again removes the receiver to complete or prepare thedesired connection, depending upon whether or not the call has beenanswered at the called substation. The other method commonly used inhandling reverting calls in automatic systems is that of providingspecial reverting call switches for selective ringing purposes. Inpracticing this method the substations associated with the party linesare provided with special numbers. These special numbers must be dialledby calling subscribers in `order to set up reverting call connections.

It is an object of the present invention to provide improved apparatusand circuits for establishing reverting call connections between thesubstations associated with the multi-party lines fof a system.

It is another object of the present invention to provide improvedreverting call signalling apparatus and circuits in a system not usingspecial reverting call control devices or switches as above mentioned,such system being of the type in which a prefix is added to the regulardirectory number and then the directory number is dialled, with the callgoing through selector and connector switches to the called line.

It is still another object of the invention to provide, in a revertingcall system of the type mentioned in the immediately precedingparagraph, apparatus and circuits for use in an automatic telephonesystem of the terminal per station type, particularly such a system asshown in Patent 1,727,133.

Further objects, features and advantages characteristic of the presentinvention will best be understood by referring to the speciiicaticntaken in connection with the accompanying drawings in which Figs. 1-5,when arranged in the order named and with correspondingly identifiedlines in alignment, show the layout (Fig. 1) and the detailed circuitsof a suiiicient portion of an automatic telephone system to enable oneskilled 2 in the art to understand the invention. The novel featureswill be set forth in the appended claims.

A general description of the arrangement of the various switches andcircuits as shown in Fig/1 will first be given, after which a detaileddescription of the operation of the system as shown in Figs. 2-5 will begiven.

It will be assumed that this is a four digit system, each station havinga thousands, a hundreds, a tens and a units digit. It will further beassumed that #19 is the prex used when setting up a reverting callconnection, i. e., the calling party, desiring to establish a connectionwith another station on the same line, dials #19. then dials thedirectory number and then hangs up the receiver. The reverting callswitch under the control of the calling subscriber on the calling linecontrols other switches by repeating (during dialling) all but the lastdigit to the switch train. When the last digit is registered. thecalling party hangs up the receiver and this last digit is repeated bythe reverting call circuit to the connector used in establishing theconnection, the connector seizes the line and rings the selectedstation. When the call is answered, the reverting call switch, thespecial first selector and the regular second selector used in thisconnection are released and may be used by another call. The connectordoes not release until the parties are through talking and hang up.

Referring to Fig. l, block diagrams and single line connections are usedto illustrate the general layout and operation of the connectionextending means of the system. The line terminates on a line circuithaving terminals in the banks of line finders (one of which isillustrated) each line finder being permanently associated with aregular rst selector as indicated. Level #2 of the regular iirstselector is illustrated as being connected to regular second selectors,it being understood that other levels of the regular first selectorbanks will lead to regular second selectors in other groups. Level #2 ofthe regular second selector banks leads to regular connectors of thesecond group, it being understood that other levels of the regularsecond selector banks will lead to other regular connector groups. Thebanks of the regular connectors lead back to the line circuits in thewell known arrangement used in dial telephone systems.

For providing reverting call service in this system, special secondselectors are connected to level #l of the regular first selector`circuits. Certain levels of the special second selectors are used forspecial services, such as calls to toll, information, wire chief and thelike, not necessary to be shown for an understanding of the presentinvention. Each terminal of level #9 of the special second selectorsleads to control equipment common to the switches comprising a revertingcall switch shown in the block diagram. The detailed circuit operationof this reverting call switch will be described with reference to Figs.2 and 3.

In setting up a reverting call connection, the calling line is extendedto the regular first selector when the call is initiated. When thecalling party dials #19 the regular rst selector selects the specialsecond selector and the special second selector selects the revertingcall switch, after which the regular directory number is dialled. Whenthe rst (thousands) digit is dialled certain circuit operations areeffective in the reverting call switch and this digit is repeated to thespecial rst selector associated with the reverting call switch. When thesecond (hundreds) digit is dialled this digit is repeated from thereverting call switch by way of the special first selector to theregular second selector selected in response to the advance of thespecial first selector to the level determined by the thousands digit,in this example #2. The regular second selector advances to the leveldetermined by the hundreds digit, in this example #2, after which aregular connector is selected for extending the connection to the calledline in the called group. When the third (tens) digit is dialled, theconnector is advanced to the level determined by the tens digit, in thisexample level #1. Now when the fourth (units) digit is dialled, thisdigit is recorded in the reverting call switch circuit but is notrepeated to the connector at this time. The calling party will now hearthe busy tone, after which the receiver at the calling station isreplaced on the switch hook. A sender associated with the reverting callswitch now repeats a replica of the units digit to the equipment forwardfrom the reverting call switch which includes the connector used in thisconnection for making connection with the terminals of the called (andcalling) line. The equipment backward from the reverting call switchwhich includes the line circuit, the line finder, the rst selector andthe special second selector are released and the line circuit of thecalling line is rendered non-busy so that the connector can connect withthis line. The connector circuit now rings the called station, afterwhich the receiver is removed at either the called or calling stationfor setting up the circuits to provide a talking circuit through theconnector. This eifects the release of the special first selector andthe regular second selector and also restores the reverting call switchto normal, ready for use on another call. In this particular example,the connector is of the type in which the release is controlled by thelast station to hang up, i. e., it will not release as long as there isa closed circuit across the line to which the connector is connected,Consequently, the connector remains in connection with the line circuitfor supplying talking battery to the connection until both the callingand the called parties hang up the receivers, at which time the circuitsare restored to normal. In using a connector of this type, i. e., therelease operation controlled by the last party to hang up, it is notnecessary to use a line circuit of the line lock-out type.

A detailed description of the operation of the system will now be given.When the calling line is extended to the terminals of the reverting callswitch, in response to dialling digits 1 and 9, a closed circuit by wayof the calling telephone elects the operation of relay CB of Fig. 2.This circuit may be traced from upper winding of relay CB, break contactof relay RC, tip trunk conductor T extending back through the specialsecond selector, the regular first selector, the line finder and theline circuit (not shown), by way of the calling line and substation inseries, over the ring side of the line, finder and selector circuitsabove mentioned to conductor R of Fig. 2 and thence through a breakcontact of relay RC and the lower winding of relay CB to Relay CB closesa circuit operating relay RD which may be traced from make contact ofrelay CB and winding of relay RD to The operation of relay CB alsocloses a circuit across the trunk conductors leading to the rst selectorassociated with the reverting call switch. This circuit may be tracedfrom the tip side of this trunk conductor TS, shown in the lowerright-hand portion of Fig. 3 and the lower lefthand portion of Fig. 4,make contact of relay CB, conductor RSI, break contact of relay PL,resistor 3RS and conductor RS to the incoming ring conductor leading tothe first selector. The detailed circuits of this first selector, aswell as the detailed circuits of the second selector selected by thisfirst selector, are not shown since they may be any of the well knownselector circuits. The dashed lines leading in from the lower left handportion of Fig. 4 to the connector indicate that these correspondingconductors from the reverting call switch are carried through first andsecond selectors to the selected connector.

The operation of relay RD closes a circuit for operating relay XAextending from lowermost make contact of relay RD, conductor II, normalcontact of the #l minor switch IMION, conductor I2 and lower winding ofrelay XA to The closure of the trunk circuit to the first selectoroperates the associated CB and RD relays (similar to the CB and RDrelays of Fig. 2), the latter relay applying (-l-) to sleeve conductorSS for holding the preceding switches connected to the reverting callswitch, since conductor SS leads back through a break contact of relayRC to incoming sleeve conductor S, which in turn extends back to thespecial second selector.

The reverting call switch is now in condition to receive the rst digitof the wanted telephone number, it being understood that it was selectedin response to the prefix 19. Since it is assumed that two impulses aretransmitted for the thousands digit, the two impulses transmitted fromthe calling telephone are repeated by relay CB of Fig. 2. Each releaseof relay CB opens up the circuit to relay RD, but this relay does notrelease during impulse transmission because of its slow actingcharacteristics. It might be pointed out at this time that the operationand release of relay XA (the release to be later described) performs nofunction at this time.

The rst release of relay CB at the beginning of the rst impulse of thethousands digit closes a circuit for operating relay SH which may betraced from (-1-), break contact of relay CB. make contact of relay RDand winding of relay SH to The operation of relay SH closes a circuitfor energizing stepping magnet IMX which may be traced from (-1-), makeYcontact of relay SH, break contact of relay DM, conductor i3 andwinding of magnet IMX to This advances the #l minor switch from itsnormal position to its number one off-normal position, the magnet IMXremaining energized until the release of relay SH at the end of thisdigit, this latter relay remaining operated until the end of the digit,no matter the number of impulses transmitted. When relay SH releases atthe end of the thousands digit, magnet IMX is de-energized, leaving the#I minor switch in its #l ofi-normal position. When the #l minor switchis advanced away from its normal position, the above described circuitto the lower winding of relay XA is opened at the oli-normal contactIMION for effecting the release of the XArelay.

Each release of relay CB transmits an impulse to the special firstselector associated with the reverting call switch by opening up theabove ldescribed circuit including conductors TS and RS extending tothis rst selector. Resistor ZRS and condenser C5 are bridged across thelowermost impulse contacts of relay CB for spark absorption purposes. Itwill thus be seen that this lowermost make contact of relay CB repeatsthe received impulses to the special first selector for causing thisswitch to select a regular second selector in the desired group.

Relay CB of the reverting call switch responds to the impulses of thehundreds digit and since it was assumed that there were two impulses inthis digit, the lowermost contact of relay CB repeats these two impulsesby way of conductors TS and RS for stepping the regular second selectorto the second level and for selecting an idle regular connector in thegroup associated with this level. At the beginning of the hundreds digittransmission by relay CB, the release of this relay again operates relaySH for again energizing magnet IMX for advancing the #l minor switch toposition 2. Now when relay CB remains energized at the endof thehundreds digit, relay SH releases for cie-energizing magnet IMX, thusleaving the #l minor switch in position 2.

When the circuit is extended through to the selected regular connector,relay CB of this connector (Fig. 4) is operated over a circuit which maybe traced from (-1-) upper winding of relay CB, break contact of relayAB, conductor TS, make contact of relay CB of Fig. 2, conductor RSI,break contact of relay PL, resistor SRS, conductor RS, break contact ofrelay AB and lower winding of relay CB to Relay CB closes a circuit foroperating relay RD of the connector extending from break contact oirelease magnet Z, conductor I4, make contact of relay CB and winding ofrelay RD to Relay RD applies potential to the master ground conductor MGfor locking and control purposes as will be later described. Relay XD ofthe connector is now operated over a circuit extending from make contactof relay RD, break contact of X oit-normal spring combination 2XON andthe lower winding of relay XD to Relay YD is likewise operated at thistime over a circuit extending from (-1-) on conductor MG, break contactof the Y off-normal spring combination 3YON and lower winding of relayYD to Relay RD applies to incoming sleeve conductor VS by way ofconductor SS for holding purposes.

In response to the dialing of the tens digit, re-V lay CB is releasedonce and then remains ener- 6 fgized, since it was Vassumed that altizis .the tens digit of trie cauce number. The release' Aof `relay CB ofthe reverting call switch closes the above described circuit foroperating relay SH and this relay in turn energizes magnet IMX over thepreviously described circuit for advancing the #l minor switch toposition 3. In position 3 a circuit is closed for operating relay DMwhich may be traced from on the #l minor switch wiper IMI, terminal 3 ofthis wiper, connection and conductor D, break contact of relay HS, breakcontact and winding of relay DM to Re- Ylay DM closes a locking circuitfor itself which may be traced from make contact of relay RD, breakcontact of relay HS, X contact of relay DM (which makes before any othercontact is switched on this relay) and winding of relay DM to It will beunderstood that conductor D is connected to terminal #3 of the #1 minorswitch because there are 4 digits in the telephone numbers in thissystem. If it is a, 5- `digit system, then this connection would be madeto terminal #4 of wiper IMI in accordance with the note appearing on theFig. 3 drawing.

The operation of relay DM closes a circuit for ythe release magnet IMZof the minor switch which may be traced from uppermost make contact ofrelay DM, break contact of relay LD, conductor I5, off-normal contactIM2ON and winding of magnet IMZ to This operates magnet IMZ forrestoring the #l minor switch to normal, after which the above describedcir cuit to the winding of magnet IMZ is opened for de-energizing thismagnet. When relay DM is operated as above described, the circuit to thewinding of magnet IMX is opened for de-energizing this magnet so that itwill not interfere with the release operation of the minor switch. Whenrelay CB remains energized at the end of the tens digit transmission,relay SH is released and a, circuit is closed for operating relay LDwhich may be traced from make contact of relay RD, break contact ofrelay HS, X contact .of relay DM, another make contact of relay DM,break contact of relay SH and winding of relay LD to Relay LD closes alocking circuit for itself which includes the above described operatingcircuit for this relay but is independent of the break contact of relaySH, thus maintaining relay LD energized when relay SH operates inresponse to the next digit. When the #l minor switch is restored tonormal, relay XA is again operated over a circuit extending from ,makecontact of relay RD, conductor Il, contact IMION in its normal position,conductor I2 and lower winding of relay XA to The transmission of thetens digit to the reverting call switch is effective to repeat thisdigit to the connector by interrupting conductors TS and RS in thepreviously described manner for advancing the connector to the firstlevel by operating magnet X over a circuit which may be traced frombreak contact of magnet Z, conductor I4, break contact of relay CB, makecontact of relay RD, make contact of relay XD, Y oinormal contact ZYONin its normal position, conductor I6 and winding of magnet X to Thecondenser and resistor connected to conductor IB are for spark absorbingpurposes. The impulse Y applied to conductor I6 from the break contactof relay CB energizes the lower winding of relay XD of the connector forlocking this relay in its operated position until the end of the tensdigit. At the end of this digit the connector switch remains at thelevel selected, Vin this example level #fand relay XD releases.

The units digit is now dialled, it being necessary in connection withthis digit to operate the #l minor switch a number of stepscorrespending to the impulses of the digit instead of the previousmethod of operating the minor Switch a number of steps corresponding tothe number of digits. Furthermore, the impulses of the units digittransmitted from the calling dial are not repeated to the connector butare stored and re-transmitted at a later time. The release of relay CBat the beginning of the rst impulse of the units digit closes thepreviously described circuit for operating relay SH and this relayremains operated during the units digit transmission and for a shortinterval of time thereafter. The release of relay CB also closes acircuit for operating the #l minor switch stepping magnet which may betraced from break contact of relay CB, make contact of relay RD, makecontact of relay LD, make contact of relay XA. make contact of relay DM,conductor I3 and winding of magnet IMX to Since the upper winding ofrelay XA is connected to this circuit leading to magnet IMX, relay XA islocked operated and, because of its slow acting characteristics, is notreleased until the release of relay SH at the end of the units digit.This circuit for holding relay XA energized as long as relay SH isenergized may be traced from (-i-), make contact of relay SH, makecontact oi relay DM, make contact and lower winding of relay XA to Theenergization of relay CB at the end of the rst impulse opens up andreleases magnet IMX. The remaining impulses of the series (two in thisexample) are effective to energize magnet IMX over the previouslydescribed circuit for advancing the minor switch to position 3 inresponse to the 3 impulses of the units digit. During this impulsetransmission, the conductors TS and RS are not interrupted because of aclosed circuit extending from conductor TS, make contact of relay LD,conductor RSI, break Contact of relay PL and resistor SRS to conductorRS. Consequently, the 3 impulses of the units digit are not repeated byrelay CB of the reverting call switch to relay CB of the connector. aswere the impulses of the tens digit.

Since the last digit of the wanted telephone number has been transmittedfrom the calling station and since this is a call back to the calledline, it now becomes necessary to give the calling party the busy toneas a signal that the receiver is to be hung up to effect the ringingoperation. This busy tone circuit may be traced from the source of busytone shown in the lower left hand portion of Fig. 3, conductor Il, breakcontact of relay XA, condenser CE, make contact of relay LD, breakcontact of relay HS and condenser C1 to the circuit leading back to thecalling line.

The receiver at the calling station is now hung up for effecting therelease of relay CB of the reverting call switch and this relay in turnopens up and releases the associated RD relay. The release of relay CBcloses a momentary circuit by way of the break contact of relay CB, makecontact of relay RD, and winding of relay SH to for operating thislatter relay, which is released when relay RD releases to open up theabove described circuit to the SH relay.

Relay RC of the reverting call switch is now operated over a circuitextending from break contact of relay CB, break contact of relay RD,make contact of relay LD and winding of relay RC to The operation ofrelay RC disconnects the calling line conductors from the CB relaywindings and also from the above described circuit to the busy tonesource. The operation of relay RC applies to common start conductor STfor starting the time release apparatus in operation if it is notalready operating. The operation of relay RC transfers the abovedescribed locking circuits for relays DM and LD from the previouslydescribed circuit to (-I) at a make contact of relay RD (in multiplewith a circuit to (-i-) at a make contact of relay SH) to extending froma break contact of relay PT, conductor I8, make contact of relay RC,break contact of relay XA, conductor 28, make contact of oi normalcombination IMION, conductor I I, break contact of relay HS, makecontact and winding of relay DM to and make contacts of relays DM and LDto the winding of the LD relay. It will be noted that this substitutelocking circuit to at the break contact of relay PT is closed before therelease of relay SH. Consequently, this momentary operation of relay SHserves to maintain (-i-) on the locking circuits for the DM and LDrelays until well after the substitute is provided. The operation ofrelay RC also connects time pulse conductor TPI to the winding of the PTrelay for time release purposes, which will be later described.

The operation of relay RC starts the operation of pulse relay PA. Thecircuit for energizing relay PA may be traced from (-i-), make contactof relay RC, conductor I9, break contact and lower winding of relay PAto At the same time that the lower winding of relay PA is energized overthis circuit, the upper winding is also energized in series withresistor IRS and condenser C4 to The two windings of relay PA arediierentially connected so that during the time that the chargingcurrent is ilowing into condenser C4, this current prevents theoperation of the PA relay until a point is reached on the condensercharging cycle where there is insuilicient current flow in the upperwinding of the relay to prevent its energlzation by means of the currentin its lower winding. The effect of this is to render relay PA slow tooperate. The operation of relay PA opens up the above described circuitto both windings of this relay for effecting its release. It will beslow to release however because of the discharge current from condenserC4 flowing through both windings of the relay in series aiding relation.When relay PA is rel leased, the above described operating circuit forthis relay is again closed and when the relay again operates, thiscircuit is opened for effecting the release of the relay. This providesa self interrupting circuit for the PA relay for causing it to operateand release at a rate for proper impulse transmission to the connectorby means of a circuit which will now be described.

The first operation of relay PA closes a circuit for operating relay PCwhich may be traced from make contact of relay RC, conductor I9, makecontact of relay PA, break contact and winding of relay PC to Relay PClocks itself operated to on conductor I9. After relay PC is operated,the release of relay PA closes a circuit for operating pulse repeatingrelay PL which may be traced from make contact of relay RC, conductorI9, break contact of relay PA, make contact of relay PC and winding ofrelay PL to The operation of relay PA opens up this circuit to the PLrelay for effecting its "release, consequently relay PL follows theoperation of the PA relay, being operated by the release of relay PA andreleased by the operation of relay PA. Variable resistor VR is connectedacross the winding of relay PL to provide proper timing of this relay.

Each operation of relay PL closes a circuit for operating the #2 minorswitch stepping magnet extending from (-1-), make contact of relay PLand winding of magnet 2MX to Consequently, the #2 minor switch will bestepped in response to the PL relay operation. Furthermore, eachoperation of relay PL opens up the above described circuit includingconductors TS and RS and, since relay CB of the reverting call switch isreleased at this time, the TS and RS conductors will be pulsed foreiecting the operation of relay CB of the connector in accordance withthe impulses transmitted by the PL relay of the reverting call switch.

Referring to the connector, each release of relay CB closes a circuitfor operating the connector in its Y or secondary direction, thiscircuit being traced from break contact of magnet Z, conductor I4, breakcontact of relay CB, make contact of relay RD, break contact of relayXD, make contact of relay YD, conductor 20 and winding of magnet Y toThe condenser and resistor connected to conductor 20 are for sparkabsorbing purposes. Conductor 2B is connected to the upper winding ofrelay YD so that this relay will remain locked operated during thisimpulse transmission after its lower winding is opened by the opening ofcontact 3YON in response to the switch taking its rst Y step. At the endof the retransmission of the units impulses to the connector switch,relay CB will remain energized long enough to permit the release ofrelay YD.

Referring back to the general description of the operation of thesystem, it will be recalled that it is necessary to release the linecircuit, the nder circuit, the regular first selector, and the specialsecond selector during the re-transmission of the units digit in orderto allow the connector to nd the called line idle. This is accomplishedby operating relay PR of the reverting call switch when the #2 minorswitch reaches the position next in advance of the position to which itis advanced by the impulses of the units digit. In this example, thiswill mean that this relay operation must be eected when the #2 minorswitch reaches position 2, since the #l minor switch is in position 3,set in this position by the 3 impulses of the units digit. A circuit isclosed when the #2 minor switch reaches position 2 for operating relayPR of the reverting call switch, this circuit being traced from #l minorswitch wiper (Ml in position 3, #2 minor switch wiper 2M2 in position 2,conductor 2|, make contact of relay RC' and winding of relay PR to Theoperation of relay PR disconnects from the circuit leading back to theincoming sleeve conductor S, including the make contact of relay RC, foreiecting the release of the line circuit, the line finder, the regularfirst selector and the special second selector, since these circuits aremaintained in their operated positions by the presence of on sleeveconductor S in the well known manner. Now when the #2 minor switch stepsfrom position 2 into position 3, the above described circuit to the PRrelay is opened for electing the release of this relay. The release ofrelay PR again applies to the incoming sleeve conductor of the revertingcall switch to make this switch test busy to other calls. It will thusbe seen that is removed from incoming conductor S for only a short time,which is long enough to release the preceding switches, after which thereverting call switch is protected against seizure. Since the receiverhas been hung up on the called line, the line circuit is in normalcondition so that the connector can seize and ring this line in a mannerwhich will now be described.

One of the functions of the relay BT is next explained. It will be notedthat the sleeve wiper of the connector, during the time that relay YD isoperated, is extended by way of conductor 22, make contact on relay YDand break contact of relay SW to the winding of the BT relay.Consequently, the winding of the BT relay is connected to the sleeveterminal of the called line with which the wiper S of the connector isbrought into contact during the interval that relay YD remains operatedafter the stepping operation of the connector in the Y direction hasbeen completed. The relay BT is used at this time to detect the presenceof busy indicating (-1-) potential on the called line sleeve terminal.

In the event that the called line is found busy, relay BT operates overthe above described circuit which is closed only so long as the YD relayis held operated (during and following the completion of the steppingoperation of the connector in the Y direction). When relay YD releases,a locking -circuit for relay BT is completed over the following circuit:the winding of relay BT, break contacts of relay SW, the break portionof the make-before-break contacts of relay YD, make contacts of relayBT, make contacts of relay RD to (-1-). Thus, as a result of detecting abusy condition, relay BT is operated and locked until the connector isreleased by the calling subscriber, at which time the above-describedlocking circuit is opened by the release of relay RD. During the timethat relay BT is locked. the operating circuit or" relay SW is opened atbreak contacts on relay BT and a circuit is completed to connect busytone to the calling `subscribers station over the following circuit: oneoi the output leads of the common busy tone source (the other of whichis grounded), the common busy tone wire, break contacts on relay YD,make contacts on relay BT, break contacts on relay SW, the upper windingof relay AB, condenser CI, the calling subscribers loop, the lowerwinding of relay CB through the 48 volt battery to the grounded busytone source lead.

Returning to the description, of the connection extended from thereverting call switch, when the called line is reached by the connectorswitch (third step in this example) the called line will not be busybecause it was cleared out, as previously described, when the #2 minorswitch took its second step, the next step preceding that which selectsthe called line. Therefore, the called line will test idle and whenrelay YD releases at the end of the units digit transmission. the BTrelay will not be operated and the sleeve wiper is disconnected from theBT relay and connected to the upper winding of the SW relay. This latterrelay will now operate over a circuit extending from make contact ofrelay RD, break contact of relay BT, upper winding of relay SW, breakcontact of relay YD, conductor 22, wiper S and associated terminal andwinding of the cut o` relay of the idle called line to Relay SW closes alocking circuit for itself which may be traced from (-1-) on conductorMG, X Contact and lower winding of relay SW Sleeve wiper S is nowconnected to (-1-) for making the called line busy and for operating thecut ofi relay of this line, this circuit extending from (-1-), makecontact of relay SW, conductor 22 and wiper SA to the sleeve of thecalled line.

When three impulses have been transmitted to the connector by the PLrelay of the reverting call switch, which relay is controlled by theintermittent operation of relay PA, it is necessary to stop the impulsetransmission because this corresponds to the number of impulses receivedfor the units digit. This is done by locking relay PA operated, whenthis relay operates with the #2 minor switch in position 3 incorrespondence with the #1 minor switch in position 3. This lockingcircuit may be traced from (-1-), wiper IMI of the #l minor switch inposition 3. wiper 2MI of the #2 minor switch in position 3, make contactand lower winding of relay PA to Since relay PA is locked operated,relay PL cannot again operate after it is released by the operation ofthe PA relay because its operating circuit is open at the lowermostbreak contact oi the PA relay. This leaves the #l and #2 minor switchesin position 3 where they remain until the call is answered to terminatethe ringing of the called station.

Ringing of the called bell is eilectecl over a circuit which will now bedescribed. With relay SW operated, (-,L-l potential is applied from oneof the common ringing interrupter relays Rl-R5 by way of jumperconnection H, ringing control terminal and wiper HS of the connectorswitch, conductor 23, break contact of relay RT, make contact of relaySW and winding of relay BT to Thus, relay BT operates as a ringingrelay, in addition to the function previously described, and is used toconnect ringing current to the called line during any one of the iiveringing intervals by the presence of the ringing control ground on wiperHS as determined by the jumper connection of terminal H. Therefore, theringing control terminal H of the individual line selected by theconnector can be cross connected to effect the operation of relay BT ofthe connector at any one of these ve ringing intervals for selecting anyone of the iive generator sources by extending the circuit from thegenerator source back by way of common generator conductor GEN,conductor 24, make contact of relay` BT, upper winding of relay RT,break contactof relay TL, break contact of relay RT, make contact ofrelay SW, conductor 25, ring wiper R and terminal of the connectorswitch, called line and substation in series, tip terminal and wiper Tof the connector switch, conductor 25, make contact of relay SW andbreak contact of relay RT to (l-l. By this arrangement (shown in theabove mentioned Patent Number 1,727,133), terminal per station operationmay be provided so that a station may be moved from one line to anotherwithout changing the station number if there is a vacancy on the line towhich the station is moved having the same frequency or code as thestation to be moved. This is because the T, R and S terminals of theconnector, associated with any line, can be cross connected to any otherline and the HS terminal can be cross connected to any frequency orcode.

In response to the answering of the call by the called party, or inresponse to the removal of the receiver by the calling party, relay RTwill be operated over a circuit including the closed path of the calledline. This circuit Will include the common generator conductor if thecall is answered during the ringing interval (with relay BT operated)and will include the circuit to by way of break contact of relay BT andmake Contact of relay RD if the call is answered during the silentinterval.

The operation of relay RT closes a locking circuit for itself extendingfrom (-1-) on conductor MG, break contact of relay TL, X make contact ofrelay RT, make contact of the continuity spring combination and lowerWinding of relay RT to This extends the line circuit through makecontacts of relay SW and make contacts of relay RT to the windings ofthe AB relay to and (-1-), the latter circuit to (-1-) extending througha make contact of relay SW. Relay AB operates and closes a circuit foroperating relay AA extending from (-1-), make contact of relay AB, makecontact of relay SW and winding of relay AA to It might be pointed outat this time that the ring back tone circuit extending from commonconductor RBT, located in the lower left hand portion of Fig. 5, by wayof condensers C3 and C2 to the calling line serves no purpose in a callof this class because the calling party has the receiver on the switchhook during this ringing operation. This RBT circuit is for use on aregular. instead of a reverting call. Likewise, talking condensers CIand C2 are only used on a regular call.

The operation of relay AA closes a circuit for operating relay HS of thereverting call switch which may be traced from (-1-), lower winding ofrelay HS, conductor HSS, lower Winding of relay TL, make contact ofrelay AA and make contact of relay RD to (-l. Relay TL is not operatedover this circuit because both of its windings are energized inopposition. Relay HS closes a locking circuit for itself extending from(-1-) ,break contact of relay PT, conductor I 8, make contact of relayRC, break Contact of relay XA. conductor 28, off normal contact IMION,conductor Il, make contact and upper winding of relay HS to Theoperation of relay HS opens up the above described locking circuits forrelays DM and LD for effecting the release of these relays. The releaseof relay LD opens up and releases relay RC and this latter relaytransfers the incoming sleeve conductor to conductor SS and (-1-) at themake contact of relay RD of the connector for maintaining the revertingcall switch busy until the release oi the RD relay of the connector.

The release of relay LD closes a circuit for operating magnet IMZ forreleasing the #l minor switch and when this switch reaches its normalposition magnet IMZ is de-energized. This release circuit may 'be tracedfrom (-1-), break contacts in series of relays RD, DM and LD, conductorI5, contact IMZON and winding of magnet IMZ to The release of relay RCcloses a similar circuit for releasing the #2 minor switch by energizingmagnet 2MZ by Way of conductor 29.

The release of relay RC also effects the release of relay PC bydisconnecting (+J from conductor I9 over which relay PC was lockedoperated. When the #l minor switch wiper IMI leaves position 3 inresponse to the release operation, the above described locking circuitfor relay PA is opened for eiiecting the release of this relay. Therelease of relay LD opens up the bridge across conductors TS and RS foreffecting the release of relay CB of the connector, which in turn opensup and releases its associated RD relay. The release of relay RDdisconnects from the above described circuit to the lower winding ofrelay HS for eiecting the release of this relay, its upper winding beingdeenergized by the release of relay RC. With relay RD of the connectorreleased and with the #2 minor switch of the reverting ca11 circuit inits normal condition, (-I-) is removed from conductor SS for removingthis potential from incoming sleeve conductor S, thus rendering thereverting call circuit selectable for another connection. Relay XD ofthe connector is operated `by the release of relay RD over a circuitwhich may be traced from (-I-l break contact of relay RD, make contactof relay BT (held energized after the ringing period over a circuit thatwill next be described) and upper winding of relay XD to It will thus beseen that the release of relay RD of the connector disconnects from thesleeve conductor SS for effecting the release of the regular secondselector and the special irst selector used in connection with thiscall. Then when relay XD operates shortly thereafter, as just explained,the SS terminal associated with this connector in the second selectorbanks is connected to (-I-) over a circuit extending from make contactof relay BT, make contact of relay XD and conductor SS, thus guardingthis connector against seizure until it is released. The circuit foroperating relay BT after the ringing period may be traced from (-1-),make contact of relay AB. make contact of relay RT, make contact ofrelay SW and winding of relay BT to Talking current is now fed to theline circuit by way of the windings of the AB relay. When both partieson the line hang up, relay AB is released for opening up and releasingrelay AA. The release of relay AB also opens up the above describedcircuit for relay BT for effecting the i release of this relay. Therelease of relay BT momentarily removes (-I-) from conductor SS leadingto the connector, but this conductor is again connected to by theoperation of the connector release magnet. The release magnet isoperated over a circuit which may be traced from (-1-) break contact ofrelay RD, break contact of relay SW, conductor 30. X and Y off normalcontacts IXON and IYON and winding of magnet Z to The operation ofmagnet Z applies (-I) to conductor SS until the switch is restored tonormal and magnet Z is released by the opening of the off normalcontacts. The release of relay AA disconnects from master groundconductor MG (this conductor being connected to (-I-l when relay AA wasoperated to prevent the release of the SW, the RT and the XD relays) forde-energizing the above described locking circuits for relays SW and RT,thus eifecting the release of these relays. The release of relay BTopens up the above described circuit for the upper winding of relay XDfor effecting the release of this relay. This places the connectorcircuit in normal condition ready for use on another call.

The time release feature of the reverting call circuit will now beexplained. With relay RC operated when the calling party hangs up thereceiver as previously described, a pulse on common conductor TPI at thebeginning of the time out period will be extended through a make contactof relay RC and conductor 3i to the lower winding of relay PT foroperating and locking this relay to (-I-) on conductor I9, this (-I-lbeing maintained on conductor I9 as long as the RC relay is operated.This operation of relay PT switches conductor I8 (which is holdingrelays DM and LD operated by way of conductors 28 and Il) from direct tocommon hold conductor H2, this latter conductor being connected to (-I)at the time that conductor TP! is pulsed and for a comparatively longtime interval thereafter. This comparatively long time interval is thatwhich will control the release of the circuits at the end thereof, ifthese circuits have not been normally released as previously described.In other words, if the circuits are not normally released within thiscomparatively long time intei-val, is removed from conductor H2 foreffecting the release of the DM and LD relays, which in turn eiiects therelease of the RC relay for releasing the connection in the previouslydescribed manner. Since this feature is not a part of the presentinvention, but is only incidental thereto, the common apparatus forcontrolling the energization of conductors TPI and H2 will not be shownor described.

Condensers C'I and C8 connected to the windings of the CB relay of thereverting call switch are for the purpose of providing a capacitivecircuit from the switches ahead to give the calling party a busy tone inthe event that the first or second selector runs into an all trunks busycondition. Resistor 4RS connected to conductor HS incoming to thereverting call switch is for a. purpose which will now be explained, butwhich has no bearing on the present invention. In case a switch handlinga call from a manual position should inadvertently land on thisreverting call circuit, this connection to through resistor RS preventsthe operation of certain means in the trunk or cord circuits and theconsequent false transmission of answering supervision. Since thisfeature is only related to the operation of a trunk call which has nopart of t'he reverting call operation, it will not 4be shown orexplained in detail. In other words, the IRS resistor and the circuit isnot related to any part of the normal circuit operation of the revertingcall system.

Relay TL of the connector is also in a circuit not used in connectionwith reverting calls. This relay is used to mark a regular call (not areverting call) through the connector from a toll position, it not beingnecessary to describe this feature for an understanding of the presentinvention.

The circuit from the common interrupter conductor INT of Fig. 4 leadingto the winding of the AA relay likewise does not function in connectionwith a reverting call, but is for the purpose of providing a flash busysignal to a manual position when a busy line is called from thisposition. This ash signal is sent back over the HSS conductor byintermittently switching this conductor from (-I) to While there hasbeen described what is at present considered to be the preferredembodiment of the invention, it will be understood that variousmodifications may be made therein without departing from the spirit ofthe invention as intended to fall within the true scope of the appendedclaims.

What I claim is:

l. In an automatic telephone system, a party line, a calling station anda called station on said line, a reverting call device, one or moreselector switches, a connector switch, means responsive to the digitalimpulses of a predetermined digit or digits received from said callingstation for setting said selector switch or switches to select saidreverting call device, means in said reverting call device responsive toa portion of the digital impulses of the directory number of said calledstation received from said calling station for re peating said portionof the received impulses to extend a connection from said reverting calldevice to said connector switch, and further means in said revertingcall device responsive to the remainder of the digital impulses of saiddirectory number for storing the last mentioned impulses for subsequenttransmission of a replica of said stored impulses to said connectorswitch.

2. In an automatic telephone system, a party line, a calling station anda called station on said line, a reverting call device, one or moreselector switches. a connector switch, means responsive to the digitalimpulses of a predetermined digit or digits received from said callingstation for setting said selector switch or switches to select saidreverting call device, means in said reverting call device responsive toa portion of the digital impulses of the directory number of said calledstation received from said calling station for repeating said portion ofthe received impulses 'to extend a connection from said reverting calldevice to said connector switch, and further means in said revertingcall device responsive to the remainder of the digital impulses of saiddirectory number for storing the last mentioned impulses, and means insaid reverting call device o controlled by said calling station fortransmitting a replica of said stored impulses to said connector switchand causing said connector switch to connect with said line and ringsaid called station.

3. In a telephone system, lines, one or more automatic switches, areverting call device, means including a calling line for directivelysetting said automatic switch or switches to extend a conn nection fromany one of Said lines to said reverting call device, one or moreadditional automatic switches, a connector switch, means controlled oversaid calling line for directively setting said additional switch orswitches to extend a connection from said reverting call device to saidconnector switch, and means in said reverting call device controlledover said calling line for controlling in the direction `backward fromsaid reverting call device said first mentioned switch or switches andcontrolling in the direction forward from said reverting call devicesaid second mentioned switch or switches to eiiect seizure of saidcalling line by said connector.

4. In a telephone system, a pluralityr of lines. a connector switch forcalling a called line, a reverting call switch, means responsive to aplurality of digital impulses transmitted from a calling station on oneof said lines for causing said connector switch to signal a station onsaid called line, and means controlled by said revert ing call switchfor holding said connector switch in connection with said called linewhen said calling station receiver is replaced on its switch hook.

5. In a telephone system, a connector switch, a dual purpose busy andringing relay in said switch having contacts for connecting busy tonecurrent to a calling line connected to said connector switch when saidswitch is calling a busy line or ringing current to a called line whensaid switch is calling an idle line, means for operating and lockingsaid relay when said connector switch calls a busy called line, andmeans for intermittently operating said relay when said connector switchcalls an idle called line.

6. In a telephone system, party lines, automatic 16 switches including afinal selector, a reverting call switch, means including said revertingcall switch effective on reverting calls between a calling and a calledsubscriber on one of said party lines for establishing a connection fromsaid reverting call switch to said called subscriber through saidautomatic switches, means responsive to the establishing of saidconnection for ringing said called subscriber, and means responsive toeither subscriber answering said ringing for releasing said revertingcall switch and all of said automatic switches except said finalselector.

'7. In a telephone system, party lines, automatic switches including afinal selector, a reverting call switch, means including said revertingcall switch effective on reverting calls between a calling and a calledsubscriber on one of said party lines for establishing a connection fromsaid reverting call switch to said called subscriber through saidautomatic switches, means responsive to the establishing of saidconnection for ringing said called subscriber, means responsive toeither subscriber answering said ringing for releasing said revertingcall switch and all of said automatic switches except said finalselector, and means controlled in response to both but not one of saidcalling or called subscribers replacing the receiver for releasing saidfinal selector.

8. In a telephone system, a plurality of subscribers lines, a pluralityof stations permanently connected to a called one of said lines, aconnector switch, a reverting call control circuit, line selecting andsignaling means associated with said connector switch, means controlledfrom a first calling station on a calling line for transmitting aplurality of digital impulses in accordance with the directory number ofa called station on said called line, means including said connectorresponsive to said plurality of digital impulses transmitted from saidplurality of first calling station for extending a connection to saidcalled line and for signaling said called station, means controlled froma second calling station on said called line for transmitting saidplurality of digital impulses in accordance with said directory numb-er,means including said connector responsive to said plurality of digitalimpulses transmitted from said second calling station for preventingsaid extension of said connection and for preventing said signaling ofsaid called station, and means controlled by said reverting call controlcircuit for cancelling said last mentioned prevent-ing means.

9. In a telephone system, a plurality of subscribers lines, a pluralityof stations permanently connected to a called one of said lines, aconnector switch, a reverting call control circuit, line selecting andsignaling means associated with said connector switch, means controlledfrom 1a rst calling station on a calling line or from a second callingstation on said called line for transmitting digital impulses inaccordance with the directory number of a called station on said calledline, means including said connector responsive to said digital impulsestransmitted fro-m said first station for extending a connection to saidcalled line and for signaling said called Station, means including saidconnector responsive to said digital impulses transmitted from saidsecond station for preventing said extension of said connection and forpreventing said signaling of said called station, and means controlledby said reverting call control circuit responsive to prefix digitalimpulses and said directory number 17 impulses for canceling said lastmentioned preventing means.

l0. In :an automatic telephone system, a connector, a plurality of linesaccessible from said connector, a reverting call control device, aplurality of sources of signaling currents, a ringing control terminalspecific to each of said lines for controlling the application of anyone of said sources of signalling current to the line associated withsaid terminal, a wiper of said connector connecting with a specificterminal when a line corresponding to` this terminal is connected to bysaid connector, relay mechanism operative to prepare a signaling currentpath to the connected line, means controlled over said specific terminalof the connected line to operate said relay mechanism in response to thetermination of the final digit of the directory number assoelated withsaid connected line, and means controlled by said reverting call controldevice for transmitting said nal digit to said connector.

11. In a telephone system, a plurality of party lines, a callingterminal for each of said lines, a reverting call switch common to saidlines, connection extending means for extending a connection from acalling one of said lines to said reverting call switch, a connectorswitch, means controlled by the calling party on said calling line forcausing said reverting call switch to set up a reverting call connectionto said calling line vla said connector switch, means including saidreverting call switch operated by the replacement of the receiver b-ysaid calling party for causing said connector switch to apply ringingcurrent to said called line indicative of the called station thereon,and means actuated by the response of said called station for cuttingoil the ringing current [and for restoring said reverting call switch tocommon use for other calls.

12. In a telephone system, a plurality of party lines, a callingterminal for each of said lines, a reverting call switch common to saidlines, rst connection extending means for extending a connection from acalling one of said lines to said reverting call switch, secondconnection extending means including a connector switch, meanscontrolled by the calling party on said calling line for causing saidreverting call switch to set up a reverting call connection to saidcalling line via said second connection extending means, means includingsaid reverting call switch operated by the replacement of the receiverby said calling party for causing said connector switch to apply ringingcurrent to said called line indicative of the called station thereon,and means actuated by the response of said called station for cuttingoff the ringing current and for restoring said reverting call switch andsaid second connection extending means except for said connector switchto common use for other calls.

13. In a telephone system, party lines, a connector switch, a revertingcall device, means exclusive of said reverting call device for extendinga rst connection from a calling station on one of said party lines tosaid connector switch, means including said reverting call device foi'extending a second connection from said calling station to saidconnector switch, means in said connector operative during said firstconnection for preventing the extension of said first connection by wayof said connector switch to said one of said party lines, and means insaid connector operative during said second connection for permittingthe extension of said second con- 18 nection by way of said connectorswitch to said one of said party lines.

14. In an automatic telephone system, a plurality of party lines, linkscommon to said lines, switching equipment arranged to connect any one ofsaid links individually to any one of said lines, control equipmentcommon to said lines and said links, means for connecting a calling oneof said lines to said control equipment, means controlled from a callingstation over said calling line for causing said common control equipmentto operate said switching equipment to link a connection between saidswitching equipment and said calling line, digit storage means in saidcommon control equipment operable over said calling line to storedigital information indicative of the designation of a desired calledstation on said calling line, means controlled by said common controlequipment in accordance with said stored digital information foroperating said switching equipment to connect to said calling line, andmeans controlled by said common control equipment in accordance withsaid stored digital information to select the proper characteristicsignal for signaling the desired station on said calling line.

15. In a reverting call switch circuit, a first switch and a secondswitch in said reverting call switch circuit, means for connecting acalling station on a calling line to said reverting call switch circuit,means controlled in response to the dialing of the digital impulses of adirectory number oi' a called station on said calling line for operatingan impulse repeating relay in said reverting call switch circuit inaccordance with said digital impulses, means controlled by said impulserepeating relay in response to certain series of said digital impulsesfor advancing a connector switch tc a level associated with said callingline and for operating said rst switch one step for each series ofdigital impulses, means for operating said second switch one step foreach impulse of the last sei'ies of said digital impulses, and meanscontrolled in accordance with the number of steps taken by said secondswitch for advancing said connector switch to said calling line.

16. In a reverting call switch circuit, a first switch and a secondswitch in said reverting call switch circuit, means for connecting acalling station on a calling line to said reverting call switch circuit,means controlled in response to the dialing of the digital impulses of adirectory number of a called station on said calling line for operatingan impulse repeating relay in said reverting call switch circuit inaccordance with said digital impulses, means controlled by said impulserepeating relay in response to all the series of said digital impulsesexcept the last for advancing a connector switch to a level associatedwith said calling line and for operating said first switch one step foreach series of digital impulses, means for operating said second switchone step for each impulse of the last series of said digital impulses,an impulse repeating device, and means controlled by said impulserepeating device in accordance with the number of steps taken by saidsecond switch for advancing said connector switch to said calling line.

1'1. In an automatic telephone system, a connector, a plurality of linesaccesible from said connector, a reverting call control device operativeto respond to digital impulses of a regular directory number of one ofsaid lines, a plurality of sources of signaling currents, a ringingcontrol terminal specific to each of said lines for controlling theapplication of any one of said sources of signaling current to the lineassociated with said terminal, a wiper of said connector connecting witha specific terminal when a line corresponding to this terminal theretois connected to by said connector, relay mechanism operative to preparea signaling current path to the connected line, means controlled oversaid specic terminal of the connected line to operate said relaymechanism in response to the termination of the final digit of thedirectory number associated with said connected line, and meanscontrolled by said reverting call control device for transmitting saidfinal digit to said connector.

18. In an automatic telephone system, a multiparty line, ringingapparatus operative to provide ringing signals having different stationindicating characteristics individually corresponding to the substationsassociated with said multi-party line, a reverting call switch circuit,automatic switching apparatus controllable over said multi-party linefrom a calling substation thereon to route a connection to saidreverting call switch circuit, means in said reverting call switchcircuit responsive to the dialing of the directory number assigned to acalled substation on said multi-party line for repeating the digitscorresponding to said directory number to automatic switching apparatusfor setting up a connection to said multiparty line, and meanscontrolled from said reverting call switch circuit for releasing aportion of said connection and for rendering said multiparty line idleto permit the application of one of said ringing signals thereto.

19. In an automatic telephone system, a multiparty line, ringingapparatus operative to provide ringing signals having different stationindicating characteristics individually corresponding to the substationsassociated with said multiparty line, a reverting call switch circuit,means for extending a connection from a calling substation on saidmulti-party line to said reverting call switch circuit, means in saidreverting call circuit responsive to the dialing of the directory numberassigned to a called substation o-n said multi-party line for repeatingthe digits corresponding to said directory number to automatic switchingapparatus for setting up a connection to said multi-party line, andmeans controlled from said reverting call switch circuit for releasing aportion of said connection and for rendering said multi-party line idleto permit tthe application of one of said ringing signals thereto.

20. In an automatic telephone system, a multiparty line, ringingapparatus operative to provide ringing signals having different stationindicating characteristics individually corresponding to the substationsassociated with said multiparty line, a reverting call switch circuit,means for extending a connection from a calling substation on saidmulti-party line to said reverting call switch circuit, means in saidreverting call* switch circuit responsive to the dialing of thedirectory number assigned to a called substationv on said multi-partyline for repeating the digits corresponding to said directory number toa selector and a connector for setting up a connection to saidmulti-party line, and means controlled from said reverting call switchcircuit for releasing said selector and for rendering said multi-partyline idle to permit said connector to connect to said multi-party lineand apply one of said signals thereto which individually corresponds tosaid called substation.

21. In a reverting call system, a reverting call switch circuit, aseries of switches comprising a switch train, a rst switch and a secondswitch in said reverting call switch circuit, means for connecting acalling station on a calling line to said reverting call switch circuit,means controlled in response to the dialing of the series of impulses ofa directory number of a called station on said calling line foroperating an impulse repeating relay in accordance with said impulses,means controlled by said impulse repeating relay in response to aportion of said series of impulses for advancing a portion of saidswitch train towards said calling line and for operating said iirstswitch one step for each series of said portion of the series ofimpulses, means controlled by said impulse repeating relay in responseto another of said series of impulses for operating said first switchone step for each impulse, a pulse generator for generating a series ofpulses, means controlled by said pulses for operating said second switchone step for each pulse, means controlled by a correspondence conditionbetween said first and said second switches for stopping said pulsegenerator, and means controlled by said pulses foi` completing theadvance of said switch train to said calling line.

22. In a reverting call system, a reverting call switch circuit, aseries of switches comprising a switch train, a first switch and asecond switch in said reverting call switch circuit, means forconnecting a calling station on a calling line to said reverting callswitch circuit, means controlled in response to the dialing of theseries of impulses of a directory number of a called station on saidcalling line for operating an impulse repeating relay in accordance withsaid impulses, means controlled by said impulse repeating relay inresponse to a portion of said series of impulses for advancing a portionof said switch train towards said calling line and for operating saidfirst switch one step for each series of said portion of the series ofimpulses, means controlled by said impulse repeating relay in responseto another of said series of impulses for operating said first switchone step for each impulse, a pulse generator for generating a series ofpulses, means controlled by said pulses for operating said second switchone step for each pulse, means controlled by a correspondence conditionbetween said iirst and said second switches for stopping said pulsegenerator, means controlled by said pulses for completing the advance ofsaid switch train to said calling line, and means controlled by astation on said line for releasing the switches in said reverting callswitch circuit.

23. In a reverting call system, a reverting call switch circuit, aseries of switches comprising a switch train, a rst switch and a secondswitch in said reverting call switch circuit, means for connecting a.calling station on a calling line to said reverting call switch circuit.means controlled in response to the dialing of the series of impulses ofa directory number of a called station on said calling line foroperating an impulse repeating relay in accordance with said impulses,means controlled by said impulse repeating relay in response to aportion of said series of impulses for advancing a portion of saidswitch train towards said calling line and for operating said irstswitch one step for each series of said portion of the series ofimpulses, means controlled by said impulse repeating relay in responseto another of said series of impulses for operating said iirst switchone step for each impulse, a pulse generator for generating a series ofpulses, means controlled by said pulses for 0D- erating said secondswitch one step for each pulse, means controlled by a correspondencecondition between said first and said second switches for stopping saidpulse generator, means controlled by said pulses for completing theadvance of said switch train to said calling line, means controlled bythe removal of the receiver at a station cn said line for releasing theswitches in said reverting call switch circuit and for releasing aportion of said switch train, and means controlled in response to thereceivers at all stations on said line being in their restored conditionafter said removal for releasing the remainder of said switch train.

24. In a telephone system; a party line; automatic switches including anal selector for calling said line; a reverting call switch; a pair ofconductors dening a talking channel; a control conductor, said talkingand control conductors inter-connecting said automatic switches and saidreverting c all switch; means in said reverting call switch responsiveto a plurality of series of impulses transmitted from a calling stationon said line for causing said final selector to signal a station on saidline; means controlled by the response of a station to said signal foreffecting the disconnection of said reverting call switch from saidinter-connection, said disconnection being controlled over said controlconductor.

25. In a telephone system, party lines, a plurality of automaticswitches including one of a plurality of connectors, said one connectorhaving line wipers for setting up a reverting call ringing connection toone of said party lines, a reverting call control circuit common to saidplurality of connectors, a ringing control wiper on said one connector,means for extending a connection from a calling line to said revertingcall control circuit, means controlled over said calling line forcausing said reverting call control circuit to set up said revertingcall ringing connection, and means including said ringing control wiperfor causing said connector to apply a distinctive ringing signal to saidparty line in accordance with the setting of said reverting call ringingconnection.

26. In a telephone system, a calling line, a party line connector of theterminal-per-station type having line wipers for setting up a connectionfrom said calling line to the terminals of a called line, a ringingcontrol wiper on said connector operated simultaneously with said linewipers, a combination ringing and busy relay in said connector, meansfor uninterruptedly operating said relay when said wipers are connectedto the terminals of a busy line for applying a busy signal to saidcalling line, an energizing circuit for said relay including saidringing control wiper, and means for intermittently operating said relayover a circuit including said ringing control wiper for ringing saidcalled line.

GEORGE ELLIOTT.

References Cited in the ille of this patent UNITED STATES PATENTS NumberName Date 1,610,438 Gardner et al. Dec. 14, 1926 1,735,378 Willis Apr.22, 1930 1,910,972 Stokely May 23, 1933 2,164,731 Bascom July 4, 19392,187,186 Wallace Jan. 16, 1940 2,335,473 Bakker Nov. 30, 1943 2,443,945Bellamy June 22, 1948

